Many types of catheters such as balloon catheters, for example, have been developed for treating problems and diseases of body systems including the vascular, pulmonary, lymphatic, urinary, and other body systems that include one or more body lumens. Such catheters advantageously provide treatment by generally minimally-invasive techniques by permitting manipulation of distal features of such catheters from their proximal ends. These catheters may be made up of many components with properties selectively chosen for specific functions. And as a result, it is generally desirable to combine different components to obtain particular control aspects of such catheters. Generally, polymeric materials are used for such catheters because of medical use conditions and sanitation requirements and the like.
Balloons for use with these catheters are frequently prepared from a variety of polymeric materials depending on their intended use. Generally, these materials are required to possess elastomeric properties such that the dilatation balloon has the requisite compliance. That is, the balloon has a predetermined relationship between balloon diameter and inflation pressure. Moreover, such balloons must be able to resist bursting at the relatively high pressures commonly employed during these procedures. Because some catheter component materials typically may not possess elastomeric properties for a particular application, the balloons can be prepared from a polymeric material which is different from, and is not readily bonded to, the material employed to fabricate the catheter.
One technique for bonding dilatation balloons and catheters involves directing laser energy along a fusion bond site. One such laser process is disclosed in U.S. Pat. No. 5,501,759 to Forman. One problem with the laser welding technique disclosed in the aforementioned patent is that it typically utilizes a predetermined static laser power over a short pulse or multiple pulses. As such, the temperature of the polymeric material rises from the beginning of the weld pulse to the end of the weld pulse in a generally linear manner. This can cause the properties of the bonded region to vary undesirably. Moreover, variations in the material contact and seam condition for individual balloon catheters may further lead to variations in the properties of the bonded region. To overcome this problem U.S. application Ser. No. 2003/0141002 employs a detector that senses thermal radiation from the bond region. The thermal radiation is correlated to the temperature of the material at the bond region. The sensed thermal radiation is utilized to provide feedback information to the laser that generates the energy that is transferred to the bond site. While this technique allows the amount of energy provided to the bond site to be dynamically adjusted based on the temperature of the bond region, it suffers from a problem that arises because the catheter and dilatation balloon are not necessarily formed from the same materials.
Accordingly, it would be desirable to provide a method and apparatus for controlling and adjusting the amount of energy that is directed to each material during the welding process.